Happydad

My 700r4 took a dump or is about to and I have a rebuilt 400 sitting around...since I don't plan to go 100+ mph and the engine is carbed so overdrive is'nt important to me...would realy like to get away from the TV cable stuff anyway..I know the drive shaft will have to be shortened but what other snags are there

Pete K

I have never pondered or did the swap. Most that go non overdrive do the turbo 350 conversion.
Tail housings will not swap, so I presume you would have to fab a crossmember to the c4's frame, then some kind of torque arm from the crossmember to the crossmember would need to be fabbed.
Hopefully, someone who has done it will chime in.
I plan to have a less expensive(hate the word cheap) trans availble for sale in the next week or 2, if that helps.

Happydad

Thanks Pete,,How easy is a 350 swap?? will things match up better..Also PM me about the trans

Pete K

I have never done the 350 swap personally, but did a little homework.
Apparently, a spacer moves the tailhousing to the proper position, allowing it to bolt directly in. Zero fabbing.
Ski_Dwn_It ran a turbo 350 for a while, and I am sure he would be helpful with some other details.
Although the tv cable is a pain in the azz, I have always been a fan of the 700. The killer 1st gear and overdrive have kept me loyal. @ $3.50 a gallon for fuel, I plan to keep mine for a while.

Demonic85

Which is faster?

Pete K

None are faster. Each one "consumes" a different amount of power.
All 3 have different gear ratio's as well. The fastest one is the one that best suits the overall combo.

CFI-EFI

While neither of the Turbo Hydro transmissions, mentioned, have a TV cable, the TH350 does have a "kick down" or detent cable. The TH400 uses an electric kick down and therefore would require a switch added onto the throttle linkage, somewhere. Just a tidbit for further consideration.

RACE ON!!!

Matt383

T400 has an elctric kick down and require a switch added onto the throttle linkage?




Matt383

CFI-EFI

AMEN!!!

From what I have observed some of the early TH400s had the switch at the carb. My GS455 Skylark had it under the dash on the gas pedal.

Believe it!

RACE ON!!!

Matt383

Now I am not a trans expert.

But I do have a T400 in my vette.

I have been in the shop when my trans was on the bench during a refresh.

All shifting and shift points are regulated by a governor (spinning weights/springs) and valve bodies (I asked a lot of questions) as I was trying to get my 1-2 and 2-3 shift dialed in.
This process was a trial and error thing until we got it right, by playing with the weights on the governor.

So I settled for getting my 1-2 shift perfect and I use a shift light for my 2-3.

Anyway, I was going to shoot my mouth off by saying that there is no electric switch until you mentioned the Skylark....

This brought back the foggy memory of a 72 cutlass I drove back when I was 16 years old. It got stuck in first gear and I had to play with cable under the dash connected to the gas pedal.
Seeing that the Buick and the cutlass were almost the same car I now can see the reason for your your explaination.

Must have been some sort of design thing they tried for a few years on those cars as I have not seen it since.

Matt383

CFI-EFI

All of mentioned shifts are up shifts. The electrical connection is for kick down.



The only cable you could have played with, under the dash, was the throttle cable. If the Cutlass had a TH350, it had the detent linkage from the carb to the trans. If it had the TH400 (it would have had a 455 engine) it would have had, I assume, from my Buick, the same switch on the gas pedal my car did. To the best of my knowledge, all the TH400s had the electrical kick down. I have three of them that do. Where's Pete K when you need him?

Matt383

Matt383

OK.
Now this is the thing.
My t400 is 1963 tecnology basically.
No electric anything.
All done mechanically... upshifts and downshifts.

wieghts, springs, valve bodies, etc.

So where is Pete K when you need him??

Matt383

CFI-EFI

No fair. I asked first. 1963??? I don't remember the first year of the TH400. I was thinking it was a couple of years later than that. One of the first was the Buick (exclusively) with the "Switch The Pitch" dual stall torque converter.

All of mine have all that you mentioned PLUS the vacuum modulator AND the electric kick down.

PETE!!!

RACE ON!!!

All2kool

When I was a Sales Manager, I would penalize employees who used the word 'cheaper'. I drove it into their heads that the term is 'more affordable'.

Matt383

[QUOTE=CFI-EFI;1561290571]No fair. I asked first.

1963??? I don't remember the first year of the TH400. I was thinking it was a couple of years later than that. One of the first was the Buick (exclusively) with the "Switch The Pitch" dual stall torque converter.

All of mine have all that you mentioned PLUS the vacuum modulator AND the electric kick down.
QUOTE]


1963..figure of speach as in old as heck. I actually think the first year was 1964 so you may be right on that.

Anyway, funny that you mention the buick.

I had to go to an old Buick yoke (1965?)
It took a larger bushing (Diameter) and was longer. (went further into tailshaft housing) for better strength and balancing.

Also, I found this bit of T400 research:

the TH400 was the first three speed, Simpson-geared automatic to use overrunning clutches for both first and second gear reaction, a feature that eliminated the need to coordinate the simultaneous release of a band and application of a clutch to make the 2-3 gear change. Owing to this feature, as well as the use of a large, multiplate clutch to provide second gear reaction, the TH400 is able to withstand very high input torque and an enormous number of shifting cycles, as would be encountered in frequent stop-and-go driving. As a result, it has met with considerable success in commercial vehicle applications.

For 1987 GM changed the nomenclature of their Turbo Hydramatic transmissions — the THM400 was renamed to the '3L80' (3 forward speeds, longitudinal positioning, and an arbitrary 'strength' of 80, the second highest such rating assigned). The 3L80HD was introduced in 1987 as the HD unit used in passenger trucks. In 1992 a 4-speed overdrive version, the 4L80-E, replaced the THM400 in Chevrolet/GMC pickups, vans, SUVs, and commercial vehicles. The 4L80E (and its successor 4L85E) was the first Hydramatic to incorporate electronic controls Matt383

Pete K

Every 400 (or turbo 375) I have come across does have an electic detent. If there are versions that do not use electric detent, I am unaware of them. The ATSG manual also makes no mention of non electric detent versions. I have always "presumed" they were all the same in this regard.

Matt383

Sorry about the bold letters.
I tried to edit them smaller but it wouldn't let me.

Matt3838

Matt383

There ya go.
I stand corrected.

Thanks Pete

Matt

CFI-EFI

OK. I'm cool with that. I thought you were being specific. I would guess 1965 or 1966.



Known as a sprag unit. It allows one member inside of another to rotate faster than the outer, but never slower than equal speed.



So now you need to go out and buy a kick down switch.

RACE ON!!!

CFI-EFI

Are you referring to the TH475 with a 2.75:1 first gear as opposed to the 2.48:1 first gear of the TH400, or is there a TH375 that I am forgetting?

RACE ON!!!